Industrial data centers have been traditionally designed to accommodate relatively large mainframe computer systems. These systems include stand-alone hinged cabinets containing central processing units, tape guide systems, disk drives, printers, control consoles, and the like. When assembled within a data center, the systems have required a relatively large amount of floor area within a given building, as well as a carefully controlled environment. Control over that environment typically requires a dedicated, sealed computer room which is serviced by corresponding dedicated air-conditioning systems. The residents of these rooms, typically computers with one or more processors, generate substantial heat during their operation. Excess heat is undesirable in this environment, as the processors work more efficiently and with lower failure rates at lowered temperatures. Because of the extensive amount of electrical interconnection required both for power supply and system communication, these computer rooms typically contain raised floors formed of tiles supported upon frames beneath which the complex cable networks can be laid. Generally, the provision of such computer rooms has represented a substantial financial investment on the part of the user. Further, the air distribution through a raised-floor plenum and air conditioning represent a significant investment, and a cooling challenge. Properly cooling these computer rooms, and their delicate residents, has proved one of the greatest challenges for designing and constructing the rooms.
In the recent past, industry has introduced processing systems employing modern, modular electronics and with supporting components permitting their rack mounted installation. Such modularized designs provide for substantial flexibility in accommodating varying processing demands. These racks are configured to accommodate computing components, networking components, and storage components, among others. Today's high compute density data center is characterized as one consisting of thousands of racks each with these networked modular computing units. The computing units include multiple microprocessors, each dissipating approximately 250 W of power. The heat dissipation from a rack containing such computing units typically exceeds 10 KW. Today's data center, with 1000 racks, spread over 30,000 square feet, requires 10 MW of power for the computing infrastructure. Tomorrow's 100,000 square foot data center will require 50 MW of power for the computing infrastructure. Energy required to dissipate this heat will be an additional 20 MW. This adds up to millions of dollars per year to power the cooling infrastructure for the data center.
A typical microprocessor system board contains one or more CPUs (central processing units) with associated cache memory, support chips, and power converters. The system board is typically mounted in a chassis containing mass storage, input/output cards, power supply and cooling hardware. Several such systems, each with maximum power dissipation of up to 300W, are mounted in a rack. The rack used in today's data center is an Electronics Industry Association (EIA) enclosure, 2 meters (78 in) high, 0.61 meter (24 in) wide and 0.76 meter (30 in) deep. A standard 2 meter rack has an available height of 40 U, where U is 44.4 mm (1.75 in). Recent market forces have driven production of 1 U high systems, such as the HEWLETT PACKARD NETSERVER LP1000. Therefore, a rack can accommodate 40 of these systems. If the power dissipation from each system board is 300 W, a single rack in a data center can be assumed to dissipate 12 KW.
The purveyor of computing services, such as an Internet service provider, installs these rack based systems in a data center. In order to maximize the compute density per unit area of the data center, there is tremendous impetus to maximize the number of systems per rack, and the number of racks per data center. If 80 half U systems were accommodated per rack the power dissipation will reach 20 KW per rack for a system board assumed to dissipate 250 W.
With the racks fully loaded, the equipment may, for example, exhibit a significantly high heat load. Moreover, the infrastructure of today must sustain the power dissipation and distribution of tomorrow. The power dissipation from computer components and systems, especially the high power density of microprocessors of the future, will require cooling solutions with unprecedented sophistication. Similarly, the units will call for an uninterrupted power supply load capacity. These requirements, particularly when more than one component of a system is utilized (a typical case) generally cannot be accommodated by the in-place air-conditioning system of a building nor its in-place power capabilities.
The general approach has been a resort to a conventional sealed computer room, an approach which essentially compromises many of the advantages of this modular form of processing system. Such computer room installations further may be called for in locations which are not owned or where the user of the systems otherwise does not have complete control over the power and air-conditioning of the system. A failure or shutdown of the cooling system can lead to computer malfunction, failure, or even permanent damage, having costly consequences for the user. In today's data centers, where air is typically the medium that transfers heat to the distant air conditioning units, large temperature gradients result in expensive cooling inefficiencies. Thus, even when these systems operate as intended, they are largely inefficient.